DIY Fermentation Temperature Controller

For the case of brewing I love the Love Controller and I will walk through a DIY that is fairly simple which will allow you to have your brews fermenting ales and lagers within 1 degree of your desired temperature. As fermentation temperature has a huge effect on the outcome of your beer, it is extremely important that this be controlled tightly.

Note: if you have no interest in making a temperature controller then go buy a Johnson Digital Controller (can be used to heat or cool):

Johnson Digital Temperature Controller

The Johnson Digital Temp Controller operates by overriding the internal thermostat in a refrigerator or freezer which gives the brewer greater control over the temperature, it can be used to heat or cool.

Mark and cutout where the controller, switch, and plugin will be installed on the unit. Also drill a hole for the power chord plugin.

Wiring schematic to controller:

Instead of wiring directly to the heater or fridge the controller should instead be wired directly to the plugins that will be installed on the electrical box. The power switch will enable the controller to then tell the switch to activate for heating or cooling depending on the mode that the controller is in (which is easily changeable).

Fermentation Where Heating is Needed:

Parts Needed:

1-Container large enough to fit a carboy in
1-Aquarium heater – and it is nice if it has suction cups to hold on to the carboy
1-Aquarium water pump

To achieve the best control I have found it is best to place the aquarium heater and pump at the bottom of the bath. On the opposite side of the carboy I place the control thermistor at the bottom of the bath. The pump will ensure good mixing when the bath is being heated and will ensure that the temperature remains constant throughout the water bath.

Fermenting Where Cooling is Needed:

Parts Needed:
1-You will need a chest freezer or fridge to place the carboy.
1-Controller Unit

Plug in the fridge to the controller unit and change the settings in the controller from heating to cooling. This is fairly straightforward and a fridge or freezer can often be found on Craigslist for free or at least for fairly cheap. Make sure to set the fridge or freezer to the lowest cooling temperature possible so it doesn’t limit your temperature range.

Unless someone tells me otherwise, I am fairly confident that this is one of the best bangs for your buck as far as home brewing is concerned right next to the wort chiller. I would never brew another batch without it.